Speedometers have been used on all types of boats for a long period of time. Speedometers serve a very important function particularly, for example, when a boat is being used for skiing because skiers are very sensitive to a change of boat speed. As a result, it is necessary to clear the pitot tube of a boat speedometer quite frequently so there may be accurate readings taken. If the speedometer should become clogged so that the driver of the boat cannot take an accurate reading, mishaps may occur, one of which can result in a skier's falling.
This invention is particularly directed to the use of pressurized gas and a series of valves to clear the pitot tube of a marine speedometer.
The known prior art consists of the following:
______________________________________ Patent No. Inventor ______________________________________ 3,349,615 Finkl 3,380,298 Hanson ______________________________________
Finkl ('615) shows a water-pressure operated boat speedometer which is supplied with a source of gas 26 which can be pressurized. Gas is introduced in the speedometer to force the water from the line and prevent corrosion and clogging. The tubes are maintained gas-filled at all times during the operation of the speedometer.
Hanson ('298) shows a device for purging the static and total pressure lines of a pitot tube. A compressor or other source of compressed gas is used to periodically purge the lines with a blast of high pressure gas. The valves are used to isolate the gauges from the high pressure source during the purge cycle. During the read cycle, the same valves isolate the high pressure source from the gauge and pitot tube lines.